Abstract
Diminished reproduction success in species with narrow distribution ranges might be one of the factors responsible for their limited dispersal and colonization abilities. We investigated here various aspects of the seed biology of the West Carpathian endemic Daphne arbuscula (Thymelaeaceae) and compared it with its more widespread relative D. cneorum. In both species, we investigated (i) differences in seed viability and germination ability; (ii) differences between the two observed fruit morphotype groups, and (iii) the effect of cold stratification in breaking seed dormancy and enhance germination in stored seeds. To determine seed viability, a tetrazolium test and an imbibed cut test were performed. Several seed germination tests with gibberellic acid and with a sequence of cold and warm stratification, using different temperatures and durations, were carried out. We uncovered that (i) D. arbuscula seeds show significantly lower viability than D. cneorum seeds, but this difference is due to the smaller-fruit morphotype; (ii) seed quality and viability of the big-fruit morphotype are significantly greater than the smaller-fruit morphotype in both species, although the seed viability of the latter is not null and the dormancy level seems to differ between them; (iii) a warm stratification at 15°C for 13 weeks, followed by cold stratification at either 0 or 5°C for 28 weeks, followed by 4 weeks at 15°C, break physiological dormancy and allow the majority of seeds of D. arbuscula (63%) to germinate. We recommend including both fruit morphotypes when collecting seed of Daphne for ex situ conservation and reintroduction initiatives, to maintain the original genetic diversity of the species.
Highlights
Members of the genus Daphne L. (Thymelaeaceae Juss.) are widely known as valuable ornamental shrubs in horticulture and as a textbook example of a genus with extensive diversification of endemic entities (Tutin 1968; Halda 2001; Yinzheng et al 2007)
We focused on Daphne arbuscula Čelak., one of the well-known narrow endemics in the genus
The viability of seeds contained in the big-fruit morphotype was very high for both species (94% in D. arbuscula, 100% in D. cneorum), and the smallerfruit morphotypes contained fewer viable seeds (58% in D. arbuscula, 86% in D. cneorum)
Summary
Members of the genus Daphne L. (Thymelaeaceae Juss.) are widely known as valuable ornamental shrubs in horticulture and as a textbook example of a genus with extensive diversification of endemic entities (Tutin 1968; Halda 2001; Yinzheng et al 2007). (Thymelaeaceae Juss.) are widely known as valuable ornamental shrubs in horticulture and as a textbook example of a genus with extensive diversification of endemic entities (Tutin 1968; Halda 2001; Yinzheng et al 2007). The genus encompasses up to 95 deciduous or evergreen shrubs native to temperate and subtropical parts of Europe, Asia and North Africa (Tutin 1968; Halda 2001). Most of the species flower in late winter or early spring with colourful, scented flowers formed by petaloid sepals forming a flower cup (hypanthium). Fruits are dry or fleshy, oneseeded drupes; zoochory is the primary dispersal mechanism (Halda 2001)
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